Flu Season Meets School Season: How Smarter Air Quality Keeps Classrooms Healthy

Every fall, classrooms fill with students—and viruses. Discover how smarter air quality strategies like low-resistance filtration, ventilation, and HEPA keep schools healthier, reduce absences, and support better learning outcomes.

Ava Montini

Aug 19, 2025

Written by

Published on

The scene every September

Every September, the school bell rings and hallways come alive again. But as backpacks and lunch boxes make their way back into classrooms, another unwelcome guest tends to sneak in too: flu season.

Teachers know it all too well. The cough that spreads from desk to desk, the hand sanitizer bottles running low by mid-morning, the spike in absenteeism that leaves lesson plans hanging. Parents know it when the inevitable call from the school office comes: “Your child has a fever, please come pick them up.”

It’s a cycle we’ve come to accept as part of the school year. But what if healthier air could help change that story?

Why flu season and school season collide

Respiratory viruses (including influenza) spread more readily indoors, where exhaled particles accumulate. That’s not speculative; CDC/NIOSH is unambiguous that better indoor ventilation reduces occupants’ overall exposure to airborne viruses. CDC

We also know influenza isn’t only about big droplets from a sneeze. People exhale infectious virus in fine aerosols during normal breathing and speaking, which can linger and travel within a room. That was demonstrated in a landmark study that detected infectious influenza virus in exhaled breath from symptomatic adults, no cough required. PNAS Nature

The drier, colder air from the fall and winter cause low humidity, helping influenza survive and transmit more efficiently. Put simply: when we bring students back into dry, tightly sealed buildings, small airborne particles build up and stay infectious longer. That’s the fixable part.

Think of clean classroom air as a budget with three line items:

Dilute what’s in the room (ventilation/outdoor air)
Remove what’s in the room (filtration/air cleaning)
Disable what’s in the room (UVGI where appropriate)

The key is using them together, sized to the space, and tuned to the school day.

What the standards now say and why it matters

Before the pandemic, most schools designed ventilation systems mainly for comfort—things like controlling odours or keeping CO₂ levels down—not for stopping the spread of illness.

That changed with ASHRAE’s new Standard 241, which focuses specifically on infection control. ASHRAE’s Standard 241: Control of Infectious Aerosols changes the target by introducing Equivalent Clean Airflow (ECA)—a flexible, additive way to hit a per-person clean air goal using any combination of ventilation, filtration, and proven air cleaning. That means a classroom can meet its target by mixing outdoor air with high-efficiency filters, HEPA units, and/or UVGI, rather than relying on outdoor air alone. ASHRAE+1

In parallel, CDC/NIOSH and EPA emphasize practical steps for schools: keep systems maintained, upgrade to MERV-13 or better where equipment allows, and supplement with portable HEPA when central systems can’t carry the whole load. CDC+1 Environmental Protection Agency

The evidence that this keeps kids in class

In a study of 162 California elementary school classrooms, illness-related absences dropped by 1.6% for every extra 1 l/s‑person of ventilation. Increasing ventilation to meet the state standard (7.1 l/s‑person) from the average (4 l/s‑person) could reduce absences by 3.4%, gain $33 million annually in attendance-based funding, while costing just $4 million more in energy.
A study across Washington and Idaho found that a 1,000 ppm increase in indoor CO₂ correlated with a 0.5–0.9% drop in average daily attendance, translating into a 10–20% rise in student absences.
In controlled environments, each 500 ppm rise in CO₂ resulted in 1.4–1.8% slower response times, along with a 2.1–2.4% lower throughput on cognitive tasks.
Harvard’s COGfx study revealed that building occupants in green-certified, well-ventilated environments scored, on average, 101% higher in cognitive tests than those in conventional buildings.

“Will MERV-13 break my units?” (The energy/airflow reality)

The honest answer: it depends on the filter you pick and your fan capacity. Research on rooftop units shows that moving from MERV-8 to MERV-13/14 can raise cooling-mode energy use by a few percent if the filter adds a lot of resistance, or it can reduce airflow if the fan can’t keep up. That’s why filter selection matters as much as efficiency.

Not all MERV-13 filters are created equal. Traditional pleated designs often create a higher pressure drop, forcing HVAC systems to work harder and sometimes leading to performance issues. But newer filtration technologies (explicitly engineered for low resistance at high efficiency, like Blade Air's Pro Filter,) are changing that equation. By combining advanced media with optimized form factors, these filters deliver MERV-13 (and higher) performance without the heavy airflow penalty.

California’s Title 24 research reinforces this point: Many modern low-pressure MERV-13 options can maintain pressure drops under 0.20 in. w.c., keeping systems within safe operating ranges. That means schools can improve air quality, meet public health guidance, and stay compliant without sacrificing system efficiency or longevity.

When you factor in the bigger picture—fewer student absences, better cognitive performance, and improved overall school operations—the ROI clearly tilts toward upgrading. Healthier air doesn’t just protect occupants; it protects the bottom line.

How this translates into a classroom target (the ECA idea)

ASHRAE 241’s Equivalent Clean Airflow lets you add up all the ways you’re cleaning air—outdoor air, central filtration, HEPA, UVGI—until you reach the per-occupant target for your space type. It’s flexible, measurable, and avoids unrealistic demands for 100% outdoor air in cold snaps. ASHRAE

A practical approach:

Estimate your current outdoor air (from design or testing).
Add the “clean air” from MERV-13 upgrades (using published efficiencies) and from each HEPA unit’s clean air delivery rate.
If the sum doesn’t meet the ECA target, add another portable unit or rethink your filtration strategy. ASHRAE

What about measurement and transparency?

CO₂ for ventilation

Track a few representative rooms across grade levels and building wings. Persistently high readings during class point to areas needing a fix (dampers, schedules, or supplemental air cleaning). Health Canada’s 1000 ppm residential benchmark is a useful anchor for conversations with families and staff. Canada.ca

PM₂.₅ for smoke days

A couple of low-drift sensors at kid-height in hallways or problem rooms can confirm your filtration strategy keeps indoor levels below outdoors during wildfire events. Health Canada and EPA both recommend this principle. Canada.ca

Bottom line

Flu season doesn’t have to mean higher absence rates and strained HVAC systems. The most effective path is a consistent program: keep ventilation tuned, use filters that balance efficiency with low resistance, and supplement with portable HEPA or UVGI where it makes sense.

The Crucial Role of Indoor Air Quality in Patient Safety: Healthcare Solutions and Strategies

Jennifer Crowley
Apr 9, 2024
4 min read

Updated: Jul 8, 2024

Image of immunocompromised patient requiring oxygen in a sanitary cleanroom at a healthcare facility — Poor IAQ can lead to the spread of airborne contaminants, including bacteria, viruses, and allergens, increasing the risk of healthcare-associated infections (HAIs) and exacerbating respiratory conditions.

In the realm of healthcare, patient safety reigns supreme. From stringent sanitation protocols to advanced medical technologies, hospitals and medical facilities spare no effort in ensuring the well-being of their patients. However, one often overlooked aspect of patient safety is the quality of the air they breathe. Indoor Air Quality (IAQ) plays a critical role in creating a safe and healthy environment for patients, staff, and visitors alike. In this blog post, we'll delve into the importance of IAQ in healthcare settings, exploring solutions and strategies to safeguard patient safety.

Understanding the Impact of IAQ on Patient Safety:

The air quality within healthcare facilities directly impacts the health outcomes of patients. Poor IAQ can lead to the spread of airborne contaminants, including bacteria, viruses, and allergens, increasing the risk of healthcare-associated infections (HAIs) and exacerbating respiratory conditions. For immunocompromised patients, such as those undergoing chemotherapy or organ transplants, exposure to pollutants in the air can pose serious health risks and hinder the healing process. Additionally, airborne particles and pollutants can trigger allergic reactions and respiratory distress in vulnerable individuals, further compromising patient safety.

Solutions for Enhancing IAQ in Healthcare Facilities:

Advanced Air Filtration Systems: Investing in high-efficiency particulate air (HEPA) filters and electrostatic precipitators can effectively capture and remove airborne pathogens and pollutants, ensuring clean and safe air for patients and staff.
Proactive Ventilation Strategies: Implementing proper ventilation systems, including increased air exchanges and the use of outdoor air intake, can help dilute indoor air pollutants and reduce the concentration of harmful contaminants.
UVC Disinfection Technology: Integrating ultraviolet germicidal irradiation (UVGI) systems into HVAC systems and air ducts can neutralize bacteria, viruses, and mold spores, providing an additional layer of protection against airborne pathogens.
Regular Maintenance and Cleaning: Routine inspection, cleaning, and maintenance of HVAC systems, air ducts, and ventilation components are essential for preventing the buildup of mold, dust, and other contaminants that can compromise IAQ.
Air Quality Monitoring: Utilizing IAQ monitoring systems and sensors allows healthcare facilities to continuously monitor air quality parameters, such as temperature, humidity, carbon dioxide levels, and volatile organic compounds (VOCs), enabling proactive identification and mitigation of IAQ issues.
Staff Education and Training: Providing healthcare staff with comprehensive training on IAQ best practices, infection control measures, and proper ventilation protocols empowers them to contribute to a safer and healthier environment for patients.

Key Spaces in Healthcare Settings to Focus IAQ Solutions on:

Patient Rooms: Ensuring clean and contaminant-free air in patient rooms is essential for protecting patients with compromised immune systems and supporting their recovery process.
Surgical Suites: Maintaining sterile environments in surgical suites is critical for preventing surgical site infections and ensuring optimal patient outcomes following surgical procedures.
Intensive Care Units (ICUs): Patients in ICUs are often the most vulnerable to airborne infections, making it imperative to implement rigorous IAQ measures to reduce the risk of cross-contamination.
Emergency Departments: High patient turnover and exposure to a wide range of illnesses in emergency departments necessitate effective IAQ solutions to minimize the spread of infectious agents.
Laboratories and Pharmacies: Controlling airborne contaminants in laboratories and pharmacies is essential for preserving the integrity of medical samples and medications and ensuring accurate test results and safe drug administration.
Waiting Areas and Common Spaces: Providing clean and comfortable air in waiting areas and common spaces enhances the overall patient experience and reduces the risk of airborne transmission of infections among patients and visitors.

Strategies for Implementing IAQ Solutions:

Assessment and Evaluation: Conducting comprehensive IAQ assessments and audits to identify potential sources of indoor air pollution and areas for improvement.
Collaboration and Stakeholder Engagement: Engaging key stakeholders, including facility managers, environmental health specialists, infection control teams, and maintenance staff, in the development and implementation of IAQ solutions fosters collaboration and ensures a coordinated approach to addressing IAQ challenges.
Prioritization of Resources: Allocating sufficient resources and budgetary support for IAQ improvement initiatives demonstrates organizational commitment to patient safety and fosters a culture of continuous improvement.
Compliance with Regulatory Standards: Adhering to IAQ regulations and guidelines set forth by regulatory agencies, such as the Environmental Protection Agency (EPA) and the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), ensures compliance and promotes accountability in maintaining safe indoor environments.
Continuous Monitoring and Evaluation: Establishing protocols for ongoing IAQ monitoring, data collection, and performance evaluation allows healthcare facilities to track progress, identify trends, and make informed decisions to optimize IAQ management strategies over time.

In the realm of healthcare, patient safety is paramount, and indoor air quality plays a crucial role in ensuring a safe and healthy environment for patients, staff, and visitors. By implementing proactive IAQ solutions and strategies, healthcare facilities can mitigate the risks associated with poor air quality, reduce the transmission of infectious diseases, and enhance overall patient outcomes.

Are you interested in learning more about Blade Air's arsenal of IAQ solutions? Connect with us so you and your patients can #BreatheEasier

As stewards of patient safety, it is incumbent upon healthcare providers to prioritize IAQ management and invest in technologies and practices that promote a clean, healthy, and healing environment for all.

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